Excited molecule polyatomic

Oref I and Tardy D 0 1990 Energy transfer in highly excited large polyatomic molecules Chem. Rev. 90 1407 5... 

Sensitivity levels more typical of kinetic studies are of the order of lO molecules cm . A schematic diagram of an apparatus for kinetic LIF measurements is shown in figure C3.I.8. A limitation of this approach is that only relative concentrations are easily measured, in contrast to absorjDtion measurements, which yield absolute concentrations. Another important limitation is that not all molecules have measurable fluorescence, as radiationless transitions can be the dominant decay route for electronic excitation in polyatomic molecules. However, the latter situation can also be an advantage in complex molecules, such as proteins, where a lack of background fluorescence allow s the selective introduction of fluorescent chromophores as probes for kinetic studies. (Tryptophan is the only strongly fluorescent amino acid naturally present in proteins, for instance.)... 

This chapter deals mainly with (multi)hyphenated techniques comprising wet sample preparation steps (e.g. SFE, SPE) and/or separation techniques (GC, SFC, HPLC, SEC, TLC, CE). Other hyphenated techniques involve thermal-spectroscopic and gas or heat extraction methods (TG, TD, HS, Py, LD, etc.). Also, spectroscopic couplings (e.g. LIBS-LIF) are of interest. Hyphenation of UV spectroscopy and mass spectrometry forms the family of laser mass-spectrometric (LAMS) methods, such as REMPI-ToFMS and MALDI-ToFMS. In REMPI-ToFMS the connecting element between UV spectroscopy and mass spectrometry is laser-induced REMPI ionisation. An intermediate state of the molecule of interest is selectively excited by absorption of a laser photon (the wavelength of a tuneable laser is set in resonance with the transition). The excited molecules are subsequently ionised by absorption of an additional laser photon. Therefore the ionisation selectivity is introduced by the resonance absorption of the first photon, i.e. by UV spectroscopy. However, conventional UV spectra of polyatomic molecules exhibit relatively broad and continuous spectral features, allowing only a medium selectivity. Supersonic jet cooling of the sample molecules (to 5-50 K) reduces the line width of their... 

V. S. Letokhov My answer to Prof. Quack is that it is indeed difficult to predict theoretically the effect of intense femtosecond IR pulses on the IVR rate of polyatomic molecules, which is important for the transfer of vibrationally excited molecules from low-lying states to the vibrational quasi-continuum. We are developing the relevant theoretical mechanisms of IR MP E/D of polyatomics since the discovery of this effect for isotopic molecules BC13 and SF6 in 1974-1975.1 hope that it will become more realistic to study experimentally the influence of intense IR pulses on IVR due to the great progress of femtosecond laser technology. 

Intermolecular energy transfer from a vibrationally excited molecule such as benzene to CCI4 could occur by two mechanisms termed direct and indirect, as diagrammed in Fig. 18. In a liquid mixture, the phonons are collective excitations of the mixture. But the coupling between intramolecular vibrations on adjacent molecules is ordinarily quite weak. Direct intermolecular transfer is important primarily in the long-lived vibrations of cryogenic liquids (7,84). In polyatomic liquid mixtures, VER... 

Interest in radiationless transitions has increased slightly in the past year. Kommandeur has provided a review with an emphasis on gas-phase problems, whilst Heller and Brown have analysed the nature of non-radiative transitions above and below crossings between potential surfaces. Collision-induced intramolecular non-radiative transitions through vibronic coupling have been calculated for medium sized molecules. The relationship between radiationless transitions and i.r. multiphoton excitation in polyatomic molecules has been theoretically investigated also radiative and non-radiative... 

R.B. Gerber and M.A. Ratner, Self-consistent field methods for vibrational excitations in polyatomic molecules, Adv. Chem. Phys., 70 (1988) 97. P. Jungwirth and R.B. Gerber, Quantum dynamics of large polyatomic systems using a classically based separable potential method, J. Chem. Phys., 102 (1995) 6046 Quantum dynamics of many atom systems by classically based separable potential (CSP) method Calculations for T (Ar),2 in full dimensionality, J. Chem. Phys., 102 (1995) 8855. 

In the next part of the section we would like to address one of our problems encountered during the study of vibrational excitations of polyatomic molecules by electron impact. The problem is related to the long-... 

Robin, M. B. In Higher Excited States ( Polyatomic Molecules Academic Press New York, 1975, Vol. 11. 

R. B. Gerber and M. Ratner, Self-consistent-field methods for vibrational excitation in polyatomic molecules, Adv. Chem. Phys. 70 97 (1988). 

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